OpenEXR 1.3.0 is a test release. The major change in this release is support for multithreaded file I/O. We've been testing the threaded code internally at ILM for a few months, and we have not encountered any bugs, but we'd like to get some feedback from others before we release the "production" version.

I encourage you to try out the new multithreading support, but be
cautious before you use it in a production environment. There are no
file format changes in this release, so the files produced by this
version should be compatible with the 1.2 series, but it's possible
that a bug in the threading code could produce invalid files. (We
have not experienced this at ILM, however.)

We don't anticipate any API changes before the production release,
either, but if we discover any problems, we may be forced to change
it.